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The sign which accompanied the PLSS.

It read

PLSS (Lunar Back Pack)

The PLSS was worn by all Apollo astronauts when on the Moon's surface. It maintained their spacesuit pressure, temperature, humidity, and proper oxygen level, as well as keeping the astronaut in constant contact with mission control.

None of the PLSSes actually used on the moon were recovered; instead they were discarded with the mission's Lunar Excursion Module (LEM), which was usually left in a low lunar orbit to eventually crash into the moon.

The PLSS on display here was the backup for the Apollo 16 mission, and would have been used on the moon if one of the two primary units had failed before launch.

Actually, the PLSSes, along with various other no-longer-needed equipment such as lunar overboots, were jettisoned while still on the lunar surface, shortly after the end of the mission's last EVA. Getting rid of unneeded equipment reduced the weight of the Lunar Module's ascent stage, allowing the astronauts to return more lunar samples and reducing the amount of fuel required to return to lunar orbit.